Automobile vehicle bodies having monocoque structure are assembled by joining a plurality of formed panels in a state where respective edge parts are overlapped on each other. Resistance spot welding, laser welding, or the like is used for the welding between the formed panels. In the automobile vehicle bodies, structural members, such as a side sill (locker), a side member, and various pillars, are joined to a portion to which a high load is applied and a portion on which a heavy load, such as an engine, is mounted. Accordingly, rigidity and strength required for the automobile vehicle bodies are guaranteed.
In recent years, it is required that the joining strength between the respective structural members and various rigidities (torsional rigidity and bending rigidity) thereof are further enhanced. Meanwhile, in order to reduce the amount of emission of greenhouse gases by virtue of improvement in fuel efficiency, further weight reduction of the respective structural members is also required.
For example, a joining structure between a side sill that is a structural member of an automobile vehicle body, and another structural member is disclosed in the following Patent Document 1. Inward flanges that are bent toward the inside of the side sill is provided at an end part of the side sill in a longitudinal direction. The side sill is joined to the other structural member (for example, a lower A pillar) via the above inward flanges.
The following Patent Document 2 discloses a vehicle side part structure including a side sill outer panel having a side sill outer part, a side sill stiffener that extends in a forward-backward direction of a vehicle body inside the side sill outer part and is joined to the side sill outer part, a rear wheel housing member having a front wall that faces a rear end of the side sill stiffener, and a coupling member having a rear wall that is connected to a rear end part of the side sill stiffener and stops up a rear end opening of the side sill stiffener, the front wall of the rear wheel housing member and a rear wall of the coupling member being joined together. According to this vehicle side part structure, rigidity on a side sill rear end side can be improved.
Moreover, the following Patent Document 3 discloses a frontside member having a frontside member main body and a kick-up part located below the frontside member main body at a rear part thereof. This frontside member is configured by butting a pair of left and right inner member and outer member against each other to perform spot welding of these members. The inner member and the outer member have upward-downward intermediate parts that are formed in a recessed shape so as to be in contact with each other. By butting the upward-downward intermediate parts against each other to perform spot welding of these intermediate parts, the frontside member is provided with a coupling part.
FIG. 22 is a view illustrating an example of the structure of a general automobile vehicle body 200. As illustrated in FIG. 22, the automobile vehicle body 200 includes a side sill (locker) 202, an A pillar (front pillar) 203, a B pillar (center pillar) 204, a roof rail 205, and the like as structural members.
With higher performance of automobiles, further enhancing the rigidity (torsional rigidity and bending rigidity) of the automobile vehicle body 200 to further improve comport, such as operation stability and silence, is required.
FIG. 23 is a perspective view illustrating an example of the side sill 202. In addition, in order to make the drawing easily understood, even in FIG. 23, a side sill inner panel 206 and a side sill outer panel 207 are illustrated in a transparent state by two-dot chain lines.
As illustrated in FIG. 23, the side sill 202 has a closed section consisting of the side sill inner panel 206, the side sill outer panel 207, a first reinforcement 208, and a second reinforcement 209.
The side sill inner panel 206 has two flanges 206a and 206b at both end parts thereof in a width direction, respectively, and has a hat-shaped cross-sectional shape having these two flanges 206a and 206b as elements.
The side sill outer panel 207 has two flanges 207a and 207b at both end parts thereof in a width direction, respectively, and has a hat-shaped cross-sectional shape having these two flanges 207a and 207b as elements.
The first reinforcement 208 is disposed between the two flanges 206a and 206b and the two flanges 207a and 207b, and is joined to the side sill inner panel 206 and the side sill outer panel 207 by welding nuggets 210 (mass of melted metal) formed by the resistance spot welding, in a state where the first reinforcement is overlapped on the side sill inner panel 206 and the side sill outer panel 207 in a three-layer overlapped manner.
The second reinforcement 209, similar to the first reinforcement 208, is also disposed between the two flanges 206a and 206b and the two flanges 207a and 207b, and is joined to the side sill inner panel 206 and the side sill outer panel 207 by the welding nuggets 210 formed by the resistance spot welding, in a state where the second reinforcement is overlapped on the side sill inner panel 206 and the side sill outer panel 207 in a three-layer overlapped manner. Moreover, the first reinforcement 208 and the second reinforcement 209 are struck (made to abut) against each other or disposed apart from each other, in the longitudinal direction of each of the side sill inner panel 206 and the side sill outer panel 207.
In addition, usually, since the welding nuggets 210 are formed at a sheet-thickness-direction central part, the welding nuggets 210 cannot be viewed from the outside. However, for convenience of description, the welding nuggets 210 are illustrated in FIG. 23 so that the positions of the welding nuggets can be recognized.
In this way, most of the structural members used for the structural bodies are assembled by welding. For this reason, in order to enhance the rigidity of the automobile vehicle body, it is effective to use linear continuous welding, such as laser welding, electric arc welding, or plasma welding. On the other hand, since the resistance spot welding that is most frequently used because of low costs as a method for welding the structural members of the automobile vehicle body is not continuous welding but dot-like discontinuous welding, this resistance spot welding is more disadvantageous in respect of the rigidity of the structural members than the continuous welding. For this reason, even if the resistance spot welding is used, techniques that can improve the rigidity of the automobile vehicle body have been developed.
For example, various kinds of structural members assembled by the resistance spot welding are disclosed in the following Patent Documents 4 to 6.